THE security forces are dealing with two possible bomb devices in south Belfast on Thursday evening.
Army technical officers have already carried out one controlled explosion duing the alert.
Police say that the security operation at Finaghy Halt will continue through the night.
A number of homes have been evacuated while some residents have stayed at home.
The alarm was raised around 3 pm and has caused serious disruption to residents and road and rail travel.
Army bomb experts were called in after a suspicious object was reported on the train lines.
Traffic has been disrupted and train services into and out of Belfast have been affected.
Finaghy Road North has been closed at its junction with Finaghy Park Central and Diamond Gardens.
Road closures are also in place at Finaghy Road North at its junction with Ardmore Park South.
A number of houses have been evacuated in the areas of Finaghy Road North, Finaghy Park Central, Finaghy Park North, Ardmore Avenue and Diamond Gardens.
The Lowe Memorial Church on the Upper Lisburn Road has been made available for evacuated residents in need of shelter.
A bus replacement service is in operation for train services between Great Victoria Street and Lisburn, and a Translink spokeswoman warned passengers to expect delays.